New Zealand has taken the top spot on a 100-nation global index of government budget transparency and accountability.

The Open Budget Survey measures the availability of eight key budget documents issued by governments, and also the comprehensiveness of the data contained in those documents.

New Zealand ranked second in the previous 2010 study. Transparency International New Zealand [Tinz] chairwoman Suzanne Snively said jumping to the top of the pile in 2012 added to the country's international profile.

"It is critical that we recognise that our leadership position is due to a long history of national vision and vigilance which must be maintained in order to sustain our international competitiveness and high quality of life," Snively said.

Many countries on the list are developing nations, and New Zealand is rated as one of only six countries that are considered to be providing "extensive" information to the public.

New Zealand's index score of 93 out of 100 was helped by the regular reporting of tax expenditures such as special tax breaks and concessions for favoured activities.

On the down-side, the country only scored "moderately well" in the public engagement section of the survey.

Tinz, which was responsible for compiling the New Zealand assessment of the survey, said there was a particular lack of public debate and independent scrutiny of the pre-budget statement.

Tinz said it was currently conducting a National Integrity Study of New Zealand which would cover possibilities for increasing public participation in fiscal policy and strengthening legal oversight.

South Africa ranked second in the Open Budget Survey, the United Kingdom was third while Sweden and Norway rounded out the top five.

The United States came in seventh, but countries such as Australia and Japan do not appear among the rankings.